[dm-devel] During systemd/udev, device-mapper trying to work with non-LVM volumes

[james harvey]

On Wed, Jul 27, 2016 at 2:49 PM, Marian Csontos <mcsontos at redhat.com> wrote:
> On 07/23/2016 01:14 AM, james harvey wrote:
>>
>> If I understand what's going on here, I think device-mapper is trying
>> to work with two volumes that don't involve LVM, causing the errors.
>
>
> If I understand correctly, these volumes DO involve LVM.
>
> It is not LV on top of your BTRFS volumes, but your BTRFS volumes are on top
> of LVM.

I do have some BTRFS volumes on top of LVM, including my 2 root
volumes, but my 2 boot partitions don't involve LVM.  They're raw disk
partitions - MD RAID 1 - BTRFS.

The kernel error references "table: 253:21" and "table: 253:22".
These entries are not referred to by running dmsetup.  If these
correspond to dm-21 and dm-22, those are the boot volumes that don't
involve LVM at all.

> Using BTRFS with thin-shapshots is not a good idea, especially, if you have
> multiple snapshots of btrfs' underlying device active.
>
> Why are you usingn BTRFS on top of thin-pool?
> BTRFS does have snapshots and IMHO you should pick either BTRFS or
> thin-pool.

I'm not using thin-snapshots, just the thin-provisioning feature.  Is
running BTRFS in that scenario still a bad situation?  Why's that?
I'm going to be using a lot of virtual machines, which is my main
reason for wanting thin-provisioning.

I'm only using btrfs snapshots.

>> Is this a device-mapper bug?  A udev bug?  Something I have configured
>> wrong?
>
> Hard to say...
>
> Which distribution?
> Kernel, lvm version?

Sorry for not mentioning.  Arch, kernel 4.6.4, lvm 2.02.161, device
mapper 1.02.131, thin-pool 1.18.0

> Ideally run `lvmdump -m` and post output, please.

The number of kernel errors during boot that I'm getting seems to be
random.  (Probably some type of race condition?)  My original post
happened to be that it was using the ones not using LVM, but sometimes
it's doing it on LVM backed volumes too.  Occasionally it gives no
kernel errors.

On this boot, I have these errors:

==========
[    3.319387] device-mapper: table: 253:5: thin: Unable to activate
thin device while pool is suspended
[    3.394258] device-mapper: table: 253:6: thin: Unable to activate
thin device while pool is suspended
[    3.632259] device-mapper: table: 253:13: thin: Unable to activate
thin device while pool is suspended
[    3.698752] device-mapper: table: 253:14: thin: Unable to activate
thin device while pool is suspended
[    4.045282] device-mapper: table: 253:21: thin: Unable to activate
thin device while pool is suspended
[    4.117778] device-mapper: table: 253:22: thin: Unable to activate
thin device while pool is suspended
==========

I've attached lvmdump-terra-snapper-2016072803258.tgz created during
the boot that gave these 6 errors.

I've also attached lvmdump-terra-snapper-2016072812433.tgz created
during a different boot, that only errors on 253:13 and 253:21.
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